Polymer capture by α-hemolysin pore upon salt concentration gradient.

Area of Science:

• Biophysics
• Nanotechnology
• Polymer Science

Background:

• Understanding polymer translocation through nanopores is crucial for applications like DNA sequencing and drug delivery.
• The α-hemolysin protein pore is a well-established model system for studying molecular transport.
• Factors like applied voltage, pH, and salt concentration gradients are known to influence translocation dynamics.

Purpose of the Study:

• To investigate the capture rate of single sodium poly(styrene sulfonate) molecules by the α-hemolysin protein pore.
• To elucidate the roles of electrostatic interactions and salt concentration gradients in polymer capture.
• To analyze how varying pH and applied voltage affects the coupling between pore-polymer interactions and translocation drift.

Main Methods:

• Single-molecule experiments measuring the capture rate of sodium poly(styrene sulfonate) by α-hemolysin.
• Systematic variation of applied voltage, pH, and salt concentration asymmetry across the pore.
• Analysis of polymer capture rate dependence on these experimental parameters.

Main Results:

• Electrostatic interactions between the polyelectrolyte and protein pore significantly impact capture rate, alongside electrolyte concentration gradient effects.
• At higher pH (repulsive interaction), an antagonistic coupling leads to non-monotonic capture rate dependence on donor salt concentration.
• At lower pH (attractive interaction), synergy with salt gradient drift results in monotonic capture rate dependence on donor salt concentration.

Conclusions:

• The interplay between electrostatic forces and salt concentration gradients dictates polymer capture dynamics in nanopores.
• Antagonistic and synergistic coupling regimes were identified, influencing the capture rate's dependence on salt concentration.
• Applied electric field strength can modulate the coupling between pore-polymer interactions and drift, affecting translocation.